Degassing light alloy melts, for example aluminum melts, is a very common activity in the casting industry. There are systems for degassing that are chemical in nature (by adding a product to the actual melt) or by means of gas bubbling. Systems based on gas bubbling include elongated ceramic elements with a porous end that are introduced into the molten metal. A very widely used variant comprises rotors, which use a rotating system which, combined with the gas injected into the metal, achieves a distribution of homogenously dispersed and very fine bubbles that entrain the impurities (primarily oxides) and gases (primarily hydrogen) present in the melt.
The device and system on which the present invention is based also operate by gas bubbling and use a source of ultrasounds in order to generate movement in the melt. The movement generated by the ultrasounds is cyclical, oscillatory and non-rotational.
Ultrasonic excitation occurs due to an oscillatory movement of a component or part, referred to as sonotrode, which amplifies the movement in the medium with which it is in contact and to which it transmits vibrations. The mentioned sonotrode, most often implemented in a cylindrical body, is responsible for transmitting the pressure waves to the fluid medium. The oscillatory movement is achieved as a result of a mechatronic system controlling the frequency and amplitude of the mentioned movement at all times.
In the case of the invention, the sonotrode is in contact with the melt, which is generally at a temperature of 800° C., and is manufactured with special materials suitable for withstanding said temperatures and, in turn, the high mechanical stress resulting from the operation thereof.
A device for degassing light alloy melts using ultrasounds is already known through patent document JP-B2-H0784626, “Method for adding ultrasonic oscillation into molten metal.” However, the device proposed in the mentioned Japanese patent does not include control means capable of recognizing the components of the sonotrode, their working conditions and, in particular, how long the sonotrode was used, and reporting to remote control equipment.
Knowing the working hours of the sonotrode is of particular interest, since the service life of the sonotrode is generally limited, i.e., about 100 hours, depending on process conditions. After this time, the sonotrode is rendered less efficient since the oscillation frequency for which it was designed changes. The change in oscillation frequency occurs due to the accelerated erosion of the sonotrode in the region which is in contact with the melt, with the subsequent loss of mass. When said problem arises, the sonotrode or a part of same must be replaced with another sonotrode or new part, in order to perform a correct or optimal degassing.